The present invention relates to a ball roller to be disposed for rotation between relatively movable parts that constitute a rolling bearing, a linear motion guide apparatus, a uniform motion joint or the like.
Such a rolling member of conventional type for use in rolling bearings may be a ball or a roller. The ball, being in point contact, may have a small load capacity but has self-aligning ability and is easy to use. The ball is endurable against thrust load equal to about one-tenth of radial load. On the other hand, the roller, being in line contact, is about six times as endurable as the ball. But as shown in FIG. 4(C), each track 110 has to have a flange 111 for supporting an end surface 103 of the roller 100. In other words, the roller 100 has to be supported at its roller surface 102 and the end surfaces 103 in the two directions, i.e., the radial and thrust directions. Thus, both the roller surface 102 in the radial direction and the end surfaces 103 in the thrust direction require an extremely special care for precise and clean finishing. The flange 111 has to be carefully formed precisely at a right angle with respect to the track 110 so that the flange 111 will be in perfect surface contact with the end surface 103 of the roller 100. In addition, a housing and a shaft to which inner and outer wheels are attached have to be precisely arranged and aligned. Frictional resistance would otherwise increase. Moreover, even if these elements are precisely formed and arranged, the tracks may deform due to load actually imposed thereon in use and the heat expansion thereof, causing the roller 100 to unevenly contact with the tracks 110 and the flanges 111 at its circular ends because the roller lacks the self-aligning ability. Furthermore, the end surfaces 103 of the roller 100 are in sliding contact with the flanges and thus receive large frictional resistance under thrust load imposed thereon. However, due to the surface contact therebetween, lubrication is usually insufficient between the contacting surfaces A of the flanges 111 and the end surfaces 103 of the roller 100, making these surfaces prone to wear and causing the roller to seize if the frictional heat becomes extremely high.